LONDON (Reuters) - The carnivorous pitcher plants that feed
on insects in the Asian tropics may not snap shut like Venus
flytraps, but they are smarter than they look.

Rather than being passive pitfall traps, the tube-like
pitchers of Nepenthes plants actually contain a clever slimy
fluid -- similar to mucus -- that produces powerful filaments
to snare prey, French researchers said on Wednesday.

The unusual qualities of the fluid could one day be used to
develop new, less environmentally harmful pesticides, the
experts believe.

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Just how pitcher plants catch their prey has intrigued
biologists since Charles Darwin's time. Until now, it was
thought that gravity and the slippery tube surface were the
key, with the fluid in the pitcher simply helping digestion.

But Laurence Gaume at the University of Montpellier and
Yoel Forterre from the University of Marseille have discovered
that the fluid actually has the perfect viscoelastic properties
to snare flies and ants.

"The elastic nature of the fluid is responsible for the
huge spring-back forces that act on moving insects," Forterre
said.

"The only chance for insects to escape the fluid would be
to move slowly. But once they've fallen in the pitchers,
insects most often panic and exhibit quick movements. It is
like swimming in jelly."

The effect is seen even when the fluid is diluted more than
90 percent with water, as can happen during heavy rainfall in
the jungles of Borneo, where many of the plants grow.

The researchers have yet to identify the molecules
responsible for the elastic properties of the fluid, which
appears to be unique in the plant kingdom. But they believe the
ingredient could help produce better pesticides in future.

Viscoelastic fluids or polymers are often added to
pesticides and herbicides to prevent sprayed droplets from
bouncing off plants, so limiting soil pollution.

The fluid from Nepenthes could provide new polymers that
are both highly effective and environmentally friendly.